Let me elaborate a little bit more....... the amd64 CAN seamlessly
switch from 32 to 64 bit morde, but you need to have an OS that
contains the libraries and headers necessary to support it. I
personally couldnt run skpe on linux on my amd64, because there is no
64 build or source code avail. I enabled this compat. mode and then
installed skype per the directions they explained and all works fine.
MythTV i was able to build for 64 natively